Wales centre Tyler Morgan suffered an ankle injury playing for the Dragons against the Ospreys last weekend.
This means that he will not take any part in Wales' end-of-year Test Series. Morgan will continue to be managed at his region.
Scarlets centre Scott Williams has been called up to join the squad on Wednesday.
Wales boss Warren Gatland initially didn't pick Willams, as well as the experienced Jamie Roberts, because he is eager to find a playmaking fly-half and inside centre combination during the upcoming internationals.
Gatland shocked critics by coaching the 2017 British and Irish Lions to a series draw in New Zealand where they implemented an exciting style of play in the Tests that revolved around the pairing of England’s Owen Farrell and Ireland’s Johnny Sexton.
Bath’s Rhys Priestland, Scarlets’ Rhys Patchell and Owen Williams of Gloucester all come into contention for Wales’ 10/12 expansive combination which Gatland is seeking to use.